Process of treating cellulose material



Patented May 24, 1932 UNITED e ascents ING CORPORATION, OF APOLLO, PENNSYLVANIA, A CORPORATION DELAWARE Pnoonss or TREATING No Drawing. Application filed June "27,

This invention relates to the manufacture of artificial silk and more'particularly to a process of treating cellulose material, such as ood pulp,-in the manufacture of artificial silk whereby the final filaments or threads produced Will possess increased Wet and dry strength. g

The principal object of this invention is to provide a process of treating cellulose ma; terial in the manufacture of artificial silk to produce a final product of superior particularly as regards to'strength, 1

Animportant object of this invention is to provide an improved method of mercerizing cellulose material particularly for use in-the manufacture ofartificial silk.

Other objects and advantagesof this invention will become apparent during the course of the followingdescription. Inmost processes heretofore employed for quality,

the manufacture of artificial silk'fibrous cellulose material is ordinarily subjected in the initial stages of the process. to a mercerizing treatment in a hot solution of caustic. A This general procedure is standard practice in the manufacture of rayon according to the socalled viscose process, Various modifications of the general procedure have been suggested and employed for various purposes. However, I have found that all of the mercerizing methods commonly employed are dispulp, to produce an alkali cellulosewhich:

advantageous in varying degrees because of the fact that partial disintegration of the cellulose due to the excessive shortening of the cellulose molecule result-s from the present practice. This disintegration eventually results in the production of artificial filaments or threads which. are insufliciently strong, particularly when in Wet'condition, to meet all of the needs of the trade. 1

I have discovered that the disintegration referred to and its resulting disadvantageous results may be materially decreased by a simple modification of the standard practice, and

it is the principal purpose of this invention to provide a simple and eflicient process of treating cellulose material, such as sulphite when treated according to standard practice of making artificial silk ill produce filaontnutosn MATERIAL 1929. Serial momma.

.filed June 27,1929, in an aqueous solutionv WILLIAM F. RICHTER, or APOLLO, PENNSYLVANIA, ASSIGNOR, r0 CHEMICAL HOLD- ofcaustic, such as sodium hydroxide, of suit able strength-for a relatively short period of time at substantially normal atmospheric temperature, Thereafter the pulp is pressed to remove the excess of-caustic, the actual amount of pressing being such that for each part of cellulose there Will remain approximately from one to three parts of caustic, computedas free caustic on a dry basis. The resulting product is then ground either in the usual manner or in the preferred manner hereinafter described for approximately two and one-halfhours, after ,Which the alkali cellulose formed is aged for approximately from tWenty-fourto forty-eight hours at or.'--

dinary atmospheric temperature. The alkali 3 cellulose thus prepared is then in condition for the customary chemical treatment to convert the cellulose' material into a spinning solution. Since this subsequent treatment forms no part of this invention per se, and since the alkali cellulose prepared may be treated according to standard practice, a specific description of the actual process of con- .verting the alkali cellulose into a spinning solution and forming such solutioninto artiflficial lsilk need not be set forth. V While numerous obvious modificationsmay be made in the process, the following specific procedure may be considered asillustrative of the invention although it is to be clearly understood that the invention is limited thereto:

not to be The cellulose fiber to be treated, such as s'ulphite pulp manufactured from spruce or poplar wood, is immersed in an aqueous solution of sodium hydroxide. Such solution containing from about 17'to 19 percent by Weight of sodiumhydroxide'. In the preferred practice of my invention an 18" per cent. solution' of i caustic. soda is employed. The amount ofcellulosematerial immersed in the caustic solution is preferably in the proportions of one part of cellulose material to from V fifteen to twenty-five, and preferably twenty,

- fifteen minutes.

tained by conducting the treatment for this. period of time, although treatment, for a parts by weight of the caustic solution, This treatment is conducted at ordinary atmospheric temperature, preferably between 17 and 20 0., for a period of approximately The best results are ob.-

greater period of time, notto exceed fortyfiv-e minutes, may be employed in some instances according to the material being treated. 'Obviously treatment for a slightly less period oftime than that indicated as the preferred time may be employed although satisfactory results are not obtained if the cellulose material is keptimmersed in the caustic solution for too short a period. I

The thus treated: material is then pressed to remove the excess of caustic soda. As

stated above, I prefer to press the material to such an extent that there will remain for each part of cellulose from one'tothree parts by measure of caustic soda computed as free caustic on a dry basis. The pressed material is then introduced into a conventional grind erwhere it is ground for a period of approximately two and one-half hours. I have found. that in grinding alkali cellulose after removal of the excess caustic it is highly advantageous to periodically reverse the direction of rotation of the grinding element.

Thus in accordance with the invention the grindingoperation is effected in repeated cycles of alternated grinding direction.

' Preferably, the grinding element is rojtated in opposite directions for relatively short periods of time, for example three minutes in one direction and then fiveminutes in the other direction, this cyclic alternating grinding being continued throughout the indicated grinding time, which usually is about two and one-half hours.

This repeatedly alternated rotation grinding procedure prevents packing of the alkali cellulose in the drum, by frequently and repeatedly breaking up the compact crumb aggregates which form-. In consequence there results a more'rapid and uniform interpenetration of'and attack by the alkali than has been the case in the prior practice, in which the grinding element isoperated continuously in one direction for about two hours, and

i then in the opposite direction during the last one-half hour.

Oneresult of my new repeatedly alternated rotation grinding is that the steeping time may be reduced to the period described above. Also, the greater uni-formity which results from such grinding reduces the time of aging. A major advantage of this procedure, in addition to the foregoing economically important benefits, is that it exerts a beneficial efiect upon: the product, by giving a rayon whose physical properties, in

both the wet and the dry condition, are improved materially over those obtained by the prior grinding procedures. The ground material which consists substantially entirely of recommend the use of the process'for' treating cotton linters, I

While I havedescribed indetail the pre ferred practice of my process, it is to be understood that the detailsof procedure may bevariously modified withoutd'ep a-rting from the spirit of the invention or the scope of the V subjoinedclaims.

What I claimis: I I v 1.. In the preparation of Viscosebytreating cellulose fiber with caustic soda and grinding the alkali cellulose thus formed, the step comprising reversing the direction of grinding at continuously repeated rel a-tivelyshort intervals of time. r

2. In the preparationof viscose, the steps com-prising treating-wood cellulose fiber with an approximately 1-8 per cent sol-ution of sodium hydroxide, removing the excess sodium hydroxide, grinding the alkali cellulose thus formed by repeatedly reversing the direction of grinding at relatively short intervals: of time until grinding is complete.

3. In the preparation of viscose by treating woodcellulose fiber with caustic soda and grinding the alkali cellulose thus formed, the step comprising repeatedly reversing thedirection of grinding at relatively short intervalsof time, and continuing such, repeated alternation of grinding direction for about two and one-half'hours. f

4-. In the preparation of viscose by treating cellulose fiber with caustic soda and grind the usual process and accordingly'I do not ing thealkal-i cellulose thus formed, the. steps comprising grinding the alkali; cellulose in one direction for about five minutes, then: reversing the direction of grinding for about three; minutes, and-continuously repeating such. reversal of grinding direction. until grinding is complete 5.. In the preparation of viscose the. steps comprising treating; cellulose fiber withan approximately 18 percent solution of sodium hydroxide at atmospheric temperature during about 15 to 45 minutes, removing thezexcess-sodilum hydroxide and grindingrthe alkali,

cellulose by repeatedly reversing the direction grinding for about three minutes, andrepeatmg such reversal of grinding direction for about two and one-half hours.

7. A process of preparing alkali cellulose for use in viscose manufacture, comprising treating a mixture of wood cellulose fiber and cotton dust the fibers of which are shorter than said wood fiber with an approximately 18% solution of sodium hydroxide, removing the excess sodium hydroxide, and grinding the thus-treated cellulose and during such grinding repeatedly reversing the direction of grindingat relatively short intervals of time. i

In testlmony whereof I aifix my signature.-

W'ILLIAM F. RICHTER. 

